The present invention relates to equipment for manufacturing a semiconductor device, particularly relates to a plasma surface processing apparatus used in a dry etching process for charging source gas in a chamber and processing the surface of semiconductor material by the physical or chemical reaction of its activated particle.
For a plasma utilizing apparatus used in the conventional manufacturing process of a semiconductor device, there is a magnetic field-provided microwave plasma etching apparatus described on pages 55 to 58 in No. 7 of "Hitachi Hyoron Vol. 76 published in 1994", for example for etching. The magnetic field-provided microwave plasma etching apparatus charges gas with an electromagnetic wave in a microwave band brought into a vacuum vessel via a magnetic field generated in a solenoid coil and a microwave circuit. As high density plasma can be obtained under low gas pressure in this conventional apparatus, a sample can be processed precisely and at a high speed. Further, a magnetic field-provided microwave plasma etching apparatus using a local magnetic field by a permanent magnet is reported for example on pages 1469 to 1471 in No. 13 of "Appl. Phys. Lett. Vol. 62 published in 1993". As a magnetic field is formed by a permanent magnet in this apparatus, both the cost of the apparatus and power consumption can be particularly reduced than those of the above conventional apparatus. In Japanese published unexamined patent application No. H3-122294, the methods of generating plasma by a high frequency in a band from 100 MHz to 1 GHz and efficient etching using a mirror field are disclosed. Further, in Japanese published unexamined patent application No. H6-224155, a method of generating uniform plasma in a chamber with a large bore diameter by a high frequency in a band of 100 to 500 MHz from an antenna in a comb shape is described.
A narrow electrode plane-parallel plate-type (hereinafter called a narrow electrode-type) apparatus is realized particularly for processing silicon oxide. Referring to the narrow electrode type, a high frequency in a band from a few teens to scores MHz is applied between plane-parallel plates apart by 1 to 2 cm to generate plasma. The narrow electrode- type apparatus is used when the pressure of source gas is scores mTorr. This narrow electrode-type apparatus is characterized in that relatively stable oxide film etching characteristics can be obtained for a long term.
In Japanese published unexamined patent application No. H7-307200, application of a high frequency in a band of approximately 300 MHz from a radial antenna with the length of one fourth of an input wavelength is described.
However, as a plurality of small-sized permanent magnets are used in the above magnetic field-provided microwave etching apparatus using a local magnetic field by a permanent magnet, the uniformity of plasma in an area in which plasma is mainly generated in the range of a magnetic field is poor and therefore, plasma is uniformed by diffusion by setting a processed sample in a position far from a plasma generated area. Therefore, there is a problem that the sufficient density of plasma cannot be obtained in a position in which a processed sample is set and a sufficient processing rate cannot be obtained.
As an electromagnetic wave is applied to a magnetic field-provided microwave plasma source from a position opposite to a sample in an electron cyclotron resonance (ECR)--type apparatus described in Japanese published unexamined patent applications No. H3-122294 and No. H6-224155, only an insulator can be formed in the position opposite to a sample. Therefore, an earth electrode required in case high frequency bias is applied to a processed sample cannot be formed in an ideal position opposite to the processed sample and there is also a problem that bias is uneven.
Further, the narrow electrode type has a problem that the directivity of the ions incident into the processed sample is uneven particularly when the width of the narrow electrode type is 0.2 .mu.m or less because the pressure of gas used for the type is relatively high, minute processability is bad and an etching rate is slow because the density of plasma is low. In the meantime, an apparatus using a so-called high density plasma source such as the ECR type and an inductive coupling type has a problem that the dissociation of source gas excessively progresses, chemical reaction in a chamber or on the surface of a wafer is difficult to control and stable etching characteristics are difficult to obtain. Particularly, as in silicon oxide etching process, the selectivity of etching is obtained by making etching and deposition compete, the badness of the controllability of reaction has an important effect upon the selectivity and the performance of the processing of a deep hole (the processing in high aspect ratio).
If an antenna in a comb shape disclosed in Japanese published unexamined patent application No. H6-224155 and a radial antenna disclosed in Japanese published unexamined patent application No. H7-307200 are used, plasma is evener than in case they are not utilized, however, sufficient uniformity cannot be obtained.